KR101028661B1 - Three-dimensional image measuring apparatus and method thereof - Google Patents

Abstract

Disclosed are a three-dimensional shape measuring apparatus and measuring method capable of shortening a measuring time. The three-dimensional shape measuring apparatus includes m projection units, an imaging unit, and a control unit. The m projections each include an illumination source and a lattice element, and the lattice elements are projected onto the measurement object every n times while transferring the lattice elements. The image forming unit photographs the lattice pattern reflected from the measurement object n × m times. The control unit controls the grid elements of at least one other projection unit to be transferred while photographing the grid pattern image using any one of the m projection units. As described above, by simultaneously performing camera imaging and lattice transfer, the measurement time of the three-dimensional shape can be greatly shortened.

Description

Three-dimensional image measuring apparatus and method

The present invention relates to a three-dimensional shape measuring apparatus and a measuring method, and more particularly to a three-dimensional shape measuring apparatus and measuring method for measuring the three-dimensional shape of the measurement object using two or more projections.

In general, techniques for measuring the three-dimensional shape of the free-form surface can be divided into contact and non-contact.

The method of measuring the entire curved shape by measuring one point on the curved surface by using a three-dimensional measuring device has been widely used for a long time, but this method has a disadvantage of excessive use of the measurement time.

In order to remedy these shortcomings, the non-contact measuring method was studied. In particular, the three-dimensional shape measuring method using the moiré phenomenon, which is one of the representative non-contact measuring methods, was first adopted by the shadow moiré method by Meadows and Takasaki in 1970. Proposed. Afterwards, Yoshino proposed a projection moiré method that can enlarge the measurement area, and the lattice, the grating and the measurement that the size of the grating used for the measurement, which was the disadvantage of the shadow moiré method, should be larger than the object to be measured. The problem of limiting the distance between waters has been solved. In addition, Kujawinska is a moiré pattern analysis method that includes three-dimensional shape information. By applying the phase shift method used for optical interference pattern analysis, the measurement resolution is remarkably improved and the measurement is not affected by the moire pattern shape. This became possible.

Recently, in order to measure a more precise three-dimensional shape, a technique of measuring a three-dimensional shape of a measurement object through two or more projection units disposed at different positions has been introduced.

1 is a view showing a three-dimensional shape measurement method using a conventional three-dimensional shape measurement apparatus. Referring to FIG. 1, when two projection units are used, conventionally, after photographing a plurality of images while transferring a grid through a first projection unit, a method of photographing a plurality of images while transferring a grid through a second projection unit The measurement was carried out.

However, due to the structure in which the grid transfer is performed after the camera imaging, the imaging time and the grid transfer time are separately required, and thus the total measurement time increases, and as the number of projections increases, the measurement time increases.

Accordingly, the present invention has been made in view of such a problem, and the present invention provides a three-dimensional shape measuring apparatus capable of shortening the measurement time of three-dimensional shape.

The present invention also provides a three-dimensional shape measuring method that can shorten the measurement time of the three-dimensional shape.

The three-dimensional shape measuring apparatus according to an aspect of the present invention includes m projections, an image forming unit, and a control unit. The m projections each include an illumination source and a grid element, and the grid pattern illumination is projected onto the measurement object every transfer while transferring the grid element n times. The image forming unit photographs a lattice pattern image reflected from the measurement object n × m times. The controller controls the grid elements of at least one other projection unit to be transferred while the grid pattern image is photographed using any one of the m projection units. N and m are two or more natural numbers.

In an embodiment, when m is 2, the controller transfers the lattice elements of the second projection unit by 2π / n while photographing the grid pattern image once using the first projection unit, and then uses the second projection unit. The grid element is transferred by 2π / n while the grid pattern image is photographed once.

In another embodiment, when m is 3 or more, the controller photographs the grid pattern image m times by using each of the first projection unit to the mth projection unit once each and simultaneously photographs itself in the m shooting periods. The lattice elements of the projections that are not used at are transferred by 2π / n during the non-photography period. In addition, the control unit may transfer its own grid element prior to at least two photographing periods before each projection unit projects the grid pattern illumination.

The controller may photograph the grid pattern image using any one of the m projection units, and then transfer the grid elements of the one projection unit to a photographing period using another projection unit immediately following.

According to the three-dimensional shape measuring method according to an aspect of the present invention, while measuring the grid-patterned illumination to the measurement object every time the grid element is transferred n times through the m projections including the illumination source and the grid element the measurement A method of measuring a three-dimensional shape by photographing a lattice pattern reflected from an object n × m times, wherein the lattice image is photographed by using any one of the m projection parts. The grid element of another projection part is conveyed. N and m are two or more natural numbers.

When m is 2, the grid element is transferred by 2π / n during the second projection unit by photographing the grid pattern image once using the first projection unit, and then the grid pattern image is transferred once using the second projection unit. The grating element of the first projection part may be transferred by 2π / n during the imaging.

When m is 3 or more, the grid pattern image is photographed m times by using the first projection unit to the mth projection unit once each, and the projection unit which is not used for photographing during the m shooting periods. The grating element can be transferred by 2π / n during the non-photography period. At this time, each projection unit may transfer its own grid element before at least two photographing periods before the projection of the grid pattern illumination.

After photographing the grid pattern image using any one of the m projection units, the grid element of any one of the projection units may be transferred during a photographing period using another projection unit immediately following.

According to such a three-dimensional shape measuring apparatus and a measuring method, the measurement time of a three-dimensional shape can be significantly shortened by simultaneously carrying out camera imaging and grid transfer. In addition, due to the shortening of the measurement time, the imaging time of the camera may be increased as needed, thereby ensuring the amount of light required for imaging.

As the inventive concept allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to the specific disclosed form, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

The terms first, second, etc. may be used to describe various elements, but the elements should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "having" are intended to indicate that there is a feature, number, step, action, component, part, or combination thereof described in the specification, and that one or more other features It should be understood that it does not exclude in advance the possibility of the presence or addition of numbers, steps, actions, components, parts or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art.

Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the meaning in the context of the relevant art and are to be interpreted as ideal or overly formal in meaning unless explicitly defined in the present application Do not.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

2 is a view schematically showing a three-dimensional shape measuring apparatus according to an embodiment of the present invention.

Referring to FIG. 2, the apparatus for measuring a three dimensional shape according to an exemplary embodiment of the present invention includes m projection units 110, an imaging unit 120, and a controller 130. M is a natural number of 2 or more.

The m projection units 110 project the grid pattern illumination onto the measurement object 150 fixed to the work stage 140, respectively. The plurality of projections 110 may be arranged to irradiate the grid-patterned light inclined at a predetermined angle with respect to the normal of the measurement object 150. For example, the three-dimensional shape measuring apparatus 100 may include two, three, four or six projections 110, the plurality of projections 110 is the normal of the measurement object 150 It can be arranged symmetrically with respect to.

Each projection unit 110 includes an illumination source 111 and a grating element 112. In addition, each projection unit 110 may further include a projection lens unit 113. The illumination source 111 irradiates light toward the measurement object 150. The grid element 112 converts the light irradiated from the illumination source 111 into grid pattern illumination according to the grid pattern. The grating element 112 is transferred n times by 2π / n through a grating transfer mechanism (not shown) such as an actuator to generate a phase shifted grating patterned light. N is a natural number of 2 or more. The projection lens 113 projects the grid-patterned light generated by the grid element 112 onto the measurement object 150. The projection lens 113 may be formed of, for example, a plurality of lens combinations, and focuses the grid-patterned light formed through the grid element 112 to project it onto the measurement object 150. Therefore, each projection unit 110 projects the grid-patterned light to the measurement object 150 every time the grid element 112 is transferred n times.

The imaging unit 120 captures a grid pattern image reflected from the measurement object 150 by the grid pattern illumination projected on the measurement object 150. Since the three-dimensional shape measuring apparatus 100 includes m projection units 110 and needs to perform n shots in each projection unit 110, the imaging unit 120 performs n × m shots. . The imaging unit 120 may include a camera 121 and an imaging lens unit 122 for capturing a grid pattern image. The camera 121 may use a CCD or CMOS camera. Therefore, the grid pattern image reflected from the measurement object 150 is photographed by the camera 121 via the imaging lens unit 122.

The controller 130 controls the operations of the components included in the 3D shape measuring apparatus 100 as a whole. The controller 130 controls the projection unit 110 to project the grid-patterned light to the measurement object 150 at every transfer while transferring the grid element 112 n times. In addition, the controller 130 controls the imaging unit 120 to photograph the grid pattern image reflected from the measurement object 150.

In particular, in order to reduce the overall measurement time of the three-dimensional shape measuring apparatus 100, the control unit 130 is to take a grid pattern image using any one of the projection unit 130 of m projection unit 110, In the meantime, the grid element 112 of the at least one other projection unit 110 is controlled to be transferred. Preferably, the controller 130 captures the grid pattern image using any one of the m projection units 110, and then, during the photographing period using another projection unit 110 immediately following the above, The grid element 112 of one projection unit 110 may be transferred by 2π / n.

3 is a view showing a driving method of a three-dimensional shape measuring apparatus including two projections.

2 and 3, the three-dimensional shape measuring apparatus 100 according to an embodiment of the present invention has two projection parts 110, that is, the first projection part 110a and the second projection part 110b. It includes.

The controller 130 controls the grid element 112 of the second projection unit, that is, the second projection unit 110b, during the photographing of the grid pattern image 1 once by using the first projection unit, that is, the first projection unit 110a. Is transferred by a length corresponding to a phase of 2π / n. Subsequently, the control unit 130 corresponds to the phase of 2π / n of the grid element 112 of the first projection unit 110a during the time of photographing the grid pattern image 2 once by using the second projection unit 110b. Transfer as long as possible. That is, the controller 130 captures the grid pattern image 1 by using the first projection unit 110a and then the grid element of the first projection unit 110a during the shooting period using the second projection unit 110b. Transfer 112. Subsequently, the control unit 130 repeats the above-described process several times through the first projection unit 110a and the second projection unit 110b to control the photographing of the grid pattern image 3 to the grid pattern image 8. .

Thereafter, the controller 130 synthesizes the grid pattern images 1, 3, 5, and 7 photographed by using the first projector 110a to obtain first phase information, and then uses the second projector 110b. After obtaining the second phase information by synthesizing the photographed grid pattern images 2, 4, 6, and 8, the 3D shape of the measurement object 150 is measured using the first phase information and the second phase information.

As described above, when the camera imaging and the lattice transfer are performed simultaneously, the measurement time can be significantly shortened as compared with the method shown in FIG. 1. In addition, due to the shortening of the measurement time, the imaging time of the camera may be increased as needed, thereby ensuring the amount of light required for imaging.

In FIG. 3, a four-bucket method of photographing four times through each projection unit 110 has been described as an example. However, the driving method described above may be applied to various buckets such as a three-bucket. .

On the other hand, when the three-dimensional shape measuring apparatus 100 includes three or more projections 110, the control unit 130 uses a grid from the first projection to the last projection, that is, the m-th projection, once each At the same time, the patterned image is photographed m times, and the grid elements of the projection unit that are not used for photographing are transported by 2π / n during the non-photographing period during the m shooting periods. For example, a driving method in the case where the three-dimensional shape measuring apparatus includes three projection units will be described with reference to FIG. 4.

4 is a view showing a method of driving a three-dimensional shape measuring apparatus according to another embodiment of the present invention.

Referring to FIG. 4, the three-dimensional shape measuring apparatus may include three projection units, that is, a first projection unit, a second projection unit, and a third projection unit. For example, it is arranged to be separated by 120 degrees around the measurement object.

During the period in which the grid-shaped image 1 is photographed using the first projection unit, that is, the first projection unit among the three projection units, one of the remaining projection units, for example, the lattice element of the third projection unit is in phase of 2π / n. Transfer it by the corresponding length. Subsequently, during the period in which the grid pattern image 2 is photographed using the second projection unit, that is, the second projection unit, one of the remaining projection units, for example, a length corresponding to a phase of 2π / n of the grid element of the first projection unit Transfer as much as possible. Thereafter, during the photographing period of the grid pattern image 3 using the third projection unit, one of the remaining projection units, for example, the grid element of the second projection unit is transferred by a length corresponding to a phase of 2π / n. Subsequently, the above process is repeated several times using the first projection unit, the second projection unit, and the third projection unit, and imaging of the grid pattern image 4 to the grid pattern image 12 is performed.

On the other hand, the transfer time of the grating element may be relatively long due to the shortening of the image photographing time. For example, when the image pickup time is about 5 ms and the transfer time of the grid element is about 7 ms, the transfer time of the grid element is about 2 ms longer than the image pickup time. In this case, since the transfer of the grating element cannot be made within one image capturing period, the transfer of the grating element is made over two image capturing periods. Therefore, it is preferable that each projection unit transfer its own grid element before at least two image pickup periods before the projection of the grid pattern lighting. For example, the first projection unit preferably transfers the grid element over two image capturing periods in which the grid pattern image 2 and the grid pattern image 3 are photographed before the grid pattern image 4 is photographed. To this end, it is preferable that each projection unit transfers its own grid element immediately after photographing the grid pattern image.

After the photographing of the grid pattern image 1 to the grid pattern image 12 is completed, the grid pattern images 1, 4, 7 and 10 photographed using the first projection unit are synthesized to obtain first phase information, and the second projection unit is used. Second phase information by synthesizing the grid pattern images 2, 5, 8, and 11 photographed using the third projection unit, and synthesizing the third phase information by synthesizing the grid pattern images 3, 6, 9, and 12 photographed using the third projection unit. After the acquisition, the three-dimensional shape of the measurement object is measured using the first phase information, the second phase information, and the third phase information.

In FIG. 4, a four-bucket method of photographing four times through each projection unit has been described as an example. However, the driving method may also be applied to various buckets such as a three-bucket. In addition, the driving method illustrated in FIG. 4 may be applied to a three-dimensional shape measuring apparatus including four or more projection units.

While the present invention has been described in connection with what is presently considered to be practical and exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit and scope of the invention. Therefore, the above description and the drawings below should be construed as illustrating the present invention, not limiting the technical spirit of the present invention.

1 is a view showing a three-dimensional shape measurement method using a conventional three-dimensional shape measurement apparatus.

2 is a view schematically showing a three-dimensional shape measuring apparatus according to an embodiment of the present invention.

3 is a view showing a driving method of a three-dimensional shape measuring apparatus including two projections.

4 is a view showing a method of driving a three-dimensional shape measuring apparatus according to another embodiment of the present invention.

<Short Description of Main Drawing Numbers>

100: three-dimensional shape measuring device 110: projection unit

111: lighting source 112: grid element

113: projection lens portion 120: the image forming portion

121: camera 122: imaging lens portion

130: control unit 140: work stage

150: measuring object

Claims (10)

M projections including an illumination source and a lattice element for projecting the lattice pattern illumination onto the measurement object during every transfer while transferring the lattice element n times; An imaging unit for photographing the lattice pattern image reflected by the measurement object n × m times; And And a control unit for controlling the grid elements of at least one other projection unit to be transferred while the grid pattern image is photographed using any one of the m projection units. Where n and m are two or more natural numbers The method of claim 1, wherein when m is 2, The control unit transfers the lattice elements of the second projection unit by 2π / n while photographing the grid pattern image once by using the first projection unit, and then, while photographing the grid pattern image once by using the second projection unit. And a lattice element of the first projection unit is transferred by 2π / n. The method of claim 1, wherein when m is 3 or more, The control unit photographs the grid pattern image m times by using the first projection unit to the mth projection unit once each, and at the same time, compares the grid elements of the projection unit that are not used for photographing during the m shooting periods. Three-dimensional shape measuring device characterized in that for transferring by 2π / n during the shooting period. The method of claim 3, The control unit is a three-dimensional shape measuring apparatus, characterized in that for transporting the grid element of its own before at least two photographing periods before each projection unit projecting the grid pattern lighting. The method of claim 1, The control unit may take the grid pattern image by using any one of the m projection units, and then transfer the lattice elements of the one projection unit to a shooting period using another projection unit immediately following. Dimensional shape measuring device. While transferring the grid elements n times through m projections including an illumination source and the grid elements, the grid pattern illumination is projected onto the measurement object every transfer, and the grid pattern image reflected from the measurement object is photographed n × m times. In the method of measuring the dimensional shape, 3. The method of claim 3, wherein the grid elements of at least one other projection part are transferred while the grid pattern image is photographed using any one of the m projection parts. Where n and m are two or more natural numbers The method of claim 6, wherein when m is 2, The lattice element of the second projection part is transferred by 2π / n while the lattice image is shot once using the first projection part, and then the lattice image is shot once using the second projection part. The three-dimensional shape measurement method characterized in that for transferring the lattice element by 2π / n. The method of claim 6, wherein when m is 3 or more, The grid patterned image was taken m times using the first projection unit to the mth projection unit once each, and the grid element of the projection unit that was not used for photographing was taken during the non-shooting period during the m shooting periods. Three-dimensional shape measurement method characterized in that the transfer by 2π / n. The method of claim 8, 3. The method of claim 3, wherein each projection unit transfers its own grid element at least two photographing periods before the projection of the grid pattern lighting. The method of claim 6, Three-dimensional shape measurement, characterized in that for shooting the grid pattern image using any one of the m projections, the grid element of any one of the projections is transferred during the shooting period using another projection immediately following Way.

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